Interpole field-magnet.



Ell wanton R. LUNDELL.

INTERPOLE FIELD MAGNET.

APPLICATION FILED FEB. 7, 1910.

J MM @513 Ethane y? ROBERT LUNDELL, OF NEW YORK, N. Y.

INTERPOLE FIELD-MAGNET.

Specification of Letters Patent.

Patented Nov. 26, 1912.

Application filed February 7, 1910. Serial No. 542,615.

improve the distribution of the field flux when the machine is workingunder full load or over-load. That is to say, the object is to cause theinterpoles to serve not only as commutating poles, but also, to someextent, as compensating poles, particularly in connection with strongarmature reactions and comparatively weak field strengths. Second, toovercome the humming noise due to the abrupt changes in themagnetization of the teeth in a slotted armature as the said teeth arepassing highly saturated pole cornerswhich noise is more or lessdifiieult to avoid in machines of ordinary construction. Third, todevise an improved lamina-ted field construction of the interpole type,which avoids the use of bolts or similar means for securing the variouspoles or pole-faces in their respective positions.

I prefer to accomplish the aforesaid objeets in connection with alaminated field magnet in which the laminations are held together enmasse in a rigid skeleton frame or crate, substantially as shown in myU. S. Patents Nos. 695,163 of March 11th, 1902, and 729,879 of June 2nd,1903.

For a full and clear understanding of the invention, such as will enableothers skilled in the art to construct the same, reference is made tothe accompanying drawings, in which,

Figure 1 is a part sectional, part end elevational view of the greaterportion of a field magnet having four main poles and four interpoles.Fig. 2 is a vertical sectional view of the field magnet illustrated inFig. 1 taken on the broken line X-Y and as seen looking thereat fromright to left. Fig. 3 is a detail view and illustrates one of theseparate main field punehings and a portion. of a drum or mandrel whichis used for the purpose of assembling said main field punehings.

Referring now to the drawings in detail, 1 represents a main sheet iron(or sheet steel) punching for the laminated field structure. Four ofthese punchings complete one layer of a field structure having four mainpoles and four interpoles. The punchings are turned over for every otherlayer in order to cause the joints to overlap in the center of the mainpoles, as clearly shown in Fig. l. 2 represents another field punchingwhich serves the purpose of completing the main poles by adding suitablepolar extensions to said main poles. These smaller punchings areassembled on top of one another to the full depth or thickness of thelaminated structure and are riveted together in a manner well known inconnection with the construction of laminated pole-faces. The endplates, between which the small punchings are riveted, may convenientlybe obtained by punching heavier material to serve as end plates or bysoldering together several of the thin punchings.

3 indicates one of :1V series of fiat strips or wedges which extendacross the entire width of the laminated structure. These strips arepreferably made of magnetic material (iron) for the purpose ofmagnetically bridging the space between the main pole tips and the endsof the interpoles. Said strips are preferably perforated for the purpose of increasing their magnetic reluctance and for improving theventilation. These strips are driven endwise into small grooves in theends of the main polar extensions and in. the lower edges of theinterpoles, substantially in the same manner that armature wedges forslotted armatures are driven into similar grooves in the armature teeth.

4 and 5 indicate cast field frames or brackets designed to rigidlysupport the laminated structure. One of these frames 4. (see Fig. 2) isfurnished with several extensions in the direction of the axis of themachine (four extensions in a four-pole structure) which extensionsserve as rigid connecting pieces between the two frames. Said frames arealso furnished with other extensions projecting radially toward thecenter oi. the machine (see 10 Fig. 2) which serve as end plates for thevarious poles.

The tlitl'crent parts of the field magnet are put together as follows:

(1.) A sutlicicnt number of the large field punchings 1 are assembled onthe mandrel 8 of Fig. 3, which mandrel is furnished with suitable keys 9for clamping or catching the small projections ti on the main poles.This mandrel with its keys will insure an accurate airgap and a perfectalinementof the laminations between the projections 6 and the catches 7.

(2) The cast field frames 4 and 5 are bolted or riveted together overthe main field punchings as indicated in Fig. 2, thereby causing saidpunchings to become firmly held under pressure in a rigid skeleton frameor crate. as shown in Figs. 1 and 2.

(3) Type metal or other suitable material is cast into the grooves 12(see Fig. 1) through suitable holes in either one of the frames 4 or 5.This operation locks the parts together and serves to compensate for anyirregularity in the punchings at their outer edges.

(4) The seats 11 (see Fig. 2) for the bearing brackets are turned out ina lathe, perfect centering being obtained by means of the mandrel 8which still remains in the field structure.

(5) The mandrel 8 is forced out in a suitable press.

(6) The various field coils (indicated by the broken lines) areassembled on their respective poles.

(7) The polar extensions which have been built up from the smallpunchings 2 are now forced into their respective places and are finallylocked by the wedges 3.

It will be understood that the above-mentioned process of constructioninsures accuracy of the airgap relative to the bearing supports, andabsolute reliability of the magnetic circuits.

Referring now to the function of the wedges 3 between the main pole tipsand the ends of the interpoles, it should first be pointed out that astrong armature reaction in combination with a comparatively weak field(for instance, such as employed in connection with the high speeds of avariable speed motor) will tend to super-saturate one of the pole tipsand annul or even reverse the polarity of the opposite pole tip.Super-saturated pole tips produce a humming noise, and a reversal of thepolarity in opposite pole tips causes the operation of a motor to becomeexceedingly unstable; The polarities of the interpoles are such thatthey tend to neutralize the above-mentioned evil effects of the armaturereactionprovided the construction is such that the lines of force fromthe inter-poles are properly conducted to the said pole tips.

The purpose of the described construction is to provide means by whichthe lines of force from the interpoles may be magnetically conducted tothe main pole tips. This is most. conveniently accomplished by makingthe wedges 3 of magnetic material. The leakage of lines of force betweenthe interpoles and the main pole tips can with this construction beadjusted to suit specific requirements. That is to say, if only a smallleakage is desired the magnetic wedges or strips 3 may be provided withholes or slots as shown in Fig. 2, thereby increasing the magneticreluctance of the said wedges.

Having thus described my invention what I claim and desire to secure byLetters Patent of the United States is- 1. A field magnet of theinterpole type having high reluctance magnetic bridgepieces between thetwo pole-tips or pole corners of a main pole and the adjacentintel-poles, said bridge-pieces extending from the extreme polar edgespractically in continuation of the pole surface, substantially as andfor the purpose described.

2. A field magnet provided with main poles and interpoles; incombination with high reluctance magnetic means for connecting the twopolar extensions of a main pole to the adjacent pole corners of theinterpoles, so that practically a continuous pole surface is obtained,substantially as de scribed.

3. A field magnet provided with main poles and interpoles, incombination with perforated connecting pieces of magnetic material forconnectlng the two pole-tips or pole corners of a main pole to theadjacent pole corners of the mterpoles, substantially as and for thepurpose described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

ROBERT LUNDELL.

Witnesses:

C. J. KINTNER, M. F. Km'rmo.

